1. Field of the Invention
This invention relates to a sewing and particularly to a sewing machine having a fabric-edge tracing function.
2. Description of the Prior Art
Fabric-edge tracing sewing machines are already known wherein stitches are formed along a line spaced by a predetermined distance from an edge of a workpiece or work fabric.
One of such fabric-edge tracing sewing machines is disclosed, for example, in Japanese Patent Laid-Open No. 221389/1987 and includes a fabric-edge sensor and a needle bar swinging mechanism. The needle bar swinging mechanism is controlled in response to a fabric-edge detection signal generated by the fabric-edge sensor so that stitches may be formed along a line spaced by a predetermined distance from an edge of a work fabric.
However, the range of swinging motion of the needle bar is limited, usually to less than 10 mm. There are several instances which may occur during sewing when the edge of the work fabric on which an edge traced seam is to be sewn is placed beyond the swinging range of the needle bar. For example, this may occur when the work fabric is first placed on the machine to begin the tracing sewing operation, when the edge to be traced is shaped or curved, or, in sewing a corner, when the needle is positioned far from the new edge to be traced after reorientation of the fabric. In these situations, stitches cannot be formed accurately and automatically at a position of the work fabric spaced by the predetermined distance from the edge of the work fabric.